High brightness light emitting diode (LED) light sources are in high demand for challenging applications including emergency lighting. Prior art in the emergency lighting field typically utilize either tungsten or tungsten halogen lamps with colored filters or, more recently, systems incorporating pre-packaged high brightness LEDs. Emergency lights are used on vehicles such as police, fire, ambulance, tow trucks, construction vehicles, plows, as well as on vehicles in the aviation and marine fields.
Generally, emergency lighting is relatively narrow in spectral width, with the most widely used colors including blue, green, amber, and red. In some cases there is a demand for white light as well. Filtered halogen or tungsten halogen lamps by the physics of their material structure and design have a wide spectral distribution ranging from the ultraviolet to well into the infrared spectrum. Thus, creating narrow spectrum single color light from tungsten or tungsten halogen lamps is very inefficient and results in limited luminance.
Prepackaged LEDs are devices comprising an LED die or die array sitting on top of one or more thermally and electrically conductive materials, each with associated thermal impedance with electrical leads and thermal backplane that are then intended to be attached to yet another board with additional thermal impedance. Examples of prepackaged devices include the Luxeon™ and Rebel™ product lines now sold by Philips, the Osram Dragon™ and Ostar™ product lines, and the CREE X-Lamp™ product line. Companies including Code 3/PSE of St. Louis, Mo. and Whelen Engineering Company of Chester, Conn., have successfully launched products incorporating prepackaged LED devices in the emergency lighting market sector.
Consequently, there is a need for high performance, low cost, compact and reliable emergency lighting, and it is a principal object of this invention to satisfy this need.
Other objects of the invention will be obvious and will in part appear hereinafter with the following detailed description is read in conjunction with the drawings.